c/r: don't require a veth link to c/r
c/r: don't require a veth link to c/r

veths can be unconnected in the container's config, and we should handle
this case.

Signed-off-by: Tycho Andersen <10c18fcb898ee6b17d6575d444b125d10b3f4d6a@canonical.com>
Acked-by: Stéphane Graber <089afc6d81f66f1168a9849e15660feae286e024@ubuntu.com>

bostjan/lxc,hallyn/lxc,fwilson42/lxc,fwilson42/lxc,thmo/lxc,federicobriata/lxc,caglar10ur/lxc,ss1h2a3tw/lxc,aeris/lxc,QingweiPeterLan/cs188-lxc,aeris/lxc,QingweiPeterLan/cs188-lxc,GreatFruitOmsk/lxc,akshaykarle/lxc,federicobriata/lxc,akshaykarle/lxc,tych0/lxc,hallyn/lxc,cjwatson/lxc,ysbnim/lxc,armcc/lxc,GreatFruitOmsk/lxc,hfuCN/lxc,ysbnim/lxc,GreatFruitOmsk/lxc,ksperis/lxc,fwilson42/lxc,federicobriata/lxc,caglar10ur/lxc,thmo/lxc,terceiro/lxc,bostjan/lxc,ysbnim/lxc,caglar10ur/lxc,Distrotech/lxc,tych0/lxc,cjwatson/lxc,LynxChaus/lxc,cjwatson/lxc,Distrotech/lxc,akshaykarle/lxc,bostjan/lxc,armcc/lxc,tych0/lxc,ksperis/lxc,aeris/lxc,hallyn/lxc,QingweiPeterLan/cs188-lxc,terceiro/lxc,ss1h2a3tw/lxc,hfuCN/lxc,LynxChaus/lxc,hfuCN/lxc,terceiro/lxc,thmo/lxc,LynxChaus/lxc,Distrotech/lxc,ss1h2a3tw/lxc,ksperis/lxc,armcc/lxc